X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fofpbuf.c;h=3de8ca5e234f535afd8bb3582c0b31d835d22b90;hb=8a9562d21a40c765a8ae6775a070cb279cb2147a;hp=bb216791b59fad3853e32a05dc9592b316994f74;hpb=c69ee87c10818267f991236201150b1fa51ae519;p=sliver-openvswitch.git

diff --git a/lib/ofpbuf.c b/lib/ofpbuf.c
index bb216791b..3de8ca5e2 100644
--- a/lib/ofpbuf.c
+++ b/lib/ofpbuf.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,29 +16,89 @@
 
 #include <config.h>
 #include "ofpbuf.h"
-#include <assert.h>
 #include <stdlib.h>
 #include <string.h>
+#include "dynamic-string.h"
+#include "netdev-dpdk.h"
 #include "util.h"
 
-/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
- * memory starting at 'base'.
- *
- * 'base' should ordinarily be the first byte of a region obtained from
- * malloc(), but in circumstances where it can be guaranteed that 'b' will
- * never need to be expanded or freed, it can be a pointer into arbitrary
- * memory. */
-void
-ofpbuf_use(struct ofpbuf *b, void *base, size_t allocated)
+static void
+ofpbuf_use__(struct ofpbuf *b, void *base, size_t allocated,
+             enum ofpbuf_source source)
 {
     b->base = b->data = base;
     b->allocated = allocated;
+    b->source = source;
     b->size = 0;
-    b->l2 = b->l3 = b->l4 = b->l7 = NULL;
-    b->next = NULL;
+    b->l2 = b->l2_5 = b->l3 = b->l4 = b->l7 = NULL;
+    list_poison(&b->list_node);
     b->private_p = NULL;
 }
 
+/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
+ * memory starting at 'base'.  'base' should be the first byte of a region
+ * obtained from malloc().  It will be freed (with free()) if 'b' is resized or
+ * freed. */
+void
+ofpbuf_use(struct ofpbuf *b, void *base, size_t allocated)
+{
+    ofpbuf_use__(b, base, allocated, OFPBUF_MALLOC);
+}
+
+/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
+ * memory starting at 'base'.  'base' should point to a buffer on the stack.
+ * (Nothing actually relies on 'base' being allocated on the stack.  It could
+ * be static or malloc()'d memory.  But stack space is the most common use
+ * case.)
+ *
+ * 'base' should be appropriately aligned.  Using an array of uint32_t or
+ * uint64_t for the buffer is a reasonable way to ensure appropriate alignment
+ * for 32- or 64-bit data.
+ *
+ * An ofpbuf operation that requires reallocating data will assert-fail if this
+ * function was used to initialize it.  Thus, one need not call ofpbuf_uninit()
+ * on an ofpbuf initialized by this function (though doing so is harmless),
+ * because it is guaranteed that 'b' does not own any heap-allocated memory. */
+void
+ofpbuf_use_stack(struct ofpbuf *b, void *base, size_t allocated)
+{
+    ofpbuf_use__(b, base, allocated, OFPBUF_STACK);
+}
+
+/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
+ * memory starting at 'base'.  'base' should point to a buffer on the stack.
+ * (Nothing actually relies on 'base' being allocated on the stack.  It could
+ * be static or malloc()'d memory.  But stack space is the most common use
+ * case.)
+ *
+ * 'base' should be appropriately aligned.  Using an array of uint32_t or
+ * uint64_t for the buffer is a reasonable way to ensure appropriate alignment
+ * for 32- or 64-bit data.
+ *
+ * An ofpbuf operation that requires reallocating data will copy the provided
+ * buffer into a malloc()'d buffer.  Thus, it is wise to call ofpbuf_uninit()
+ * on an ofpbuf initialized by this function, so that if it expanded into the
+ * heap, that memory is freed. */
+void
+ofpbuf_use_stub(struct ofpbuf *b, void *base, size_t allocated)
+{
+    ofpbuf_use__(b, base, allocated, OFPBUF_STUB);
+}
+
+/* Initializes 'b' as an ofpbuf whose data starts at 'data' and continues for
+ * 'size' bytes.  This is appropriate for an ofpbuf that will be used to
+ * inspect existing data, without moving it around or reallocating it, and
+ * generally without modifying it at all.
+ *
+ * An ofpbuf operation that requires reallocating data will assert-fail if this
+ * function was used to initialize it. */
+void
+ofpbuf_use_const(struct ofpbuf *b, const void *data, size_t size)
+{
+    ofpbuf_use__(b, CONST_CAST(void *, data), size, OFPBUF_STACK);
+    b->size = size;
+}
+
 /* Initializes 'b' as an empty ofpbuf with an initial capacity of 'size'
  * bytes. */
 void
@@ -49,13 +109,27 @@ ofpbuf_init(struct ofpbuf *b, size_t size)
 
 /* Frees memory that 'b' points to. */
 void
-ofpbuf_uninit(struct ofpbuf *b) 
+ofpbuf_uninit(struct ofpbuf *b)
 {
     if (b) {
-        free(b->base);
+        if (b->source == OFPBUF_MALLOC) {
+            free(b->base);
+        }
+        if (b->source == OFPBUF_DPDK) {
+            free_dpdk_buf(b);
+        }
     }
 }
 
+/* Returns a pointer that may be passed to free() to accomplish the same thing
+ * as ofpbuf_uninit(b).  The return value is a null pointer if ofpbuf_uninit()
+ * would not free any memory. */
+void *
+ofpbuf_get_uninit_pointer(struct ofpbuf *b)
+{
+    return b && b->source == OFPBUF_MALLOC ? b->base : NULL;
+}
+
 /* Frees memory that 'b' points to and allocates a new ofpbuf */
 void
 ofpbuf_reinit(struct ofpbuf *b, size_t size)
@@ -74,23 +148,78 @@ ofpbuf_new(size_t size)
     return b;
 }
 
+/* Creates and returns a new ofpbuf with an initial capacity of 'size +
+ * headroom' bytes, reserving the first 'headroom' bytes as headroom. */
+struct ofpbuf *
+ofpbuf_new_with_headroom(size_t size, size_t headroom)
+{
+    struct ofpbuf *b = ofpbuf_new(size + headroom);
+    ofpbuf_reserve(b, headroom);
+    return b;
+}
+
+/* Creates and returns a new ofpbuf that initially contains a copy of the
+ * 'buffer->size' bytes of data starting at 'buffer->data' with no headroom or
+ * tailroom. */
 struct ofpbuf *
 ofpbuf_clone(const struct ofpbuf *buffer)
 {
-    return ofpbuf_clone_data(buffer->data, buffer->size);
+    return ofpbuf_clone_with_headroom(buffer, 0);
+}
+
+/* Creates and returns a new ofpbuf whose data are copied from 'buffer'.   The
+ * returned ofpbuf will additionally have 'headroom' bytes of headroom. */
+struct ofpbuf *
+ofpbuf_clone_with_headroom(const struct ofpbuf *buffer, size_t headroom)
+{
+    struct ofpbuf *new_buffer;
+    uintptr_t data_delta;
+
+    new_buffer = ofpbuf_clone_data_with_headroom(buffer->data, buffer->size,
+                                                 headroom);
+    data_delta = (char *) new_buffer->data - (char *) buffer->data;
+
+    if (buffer->l2) {
+        new_buffer->l2 = (char *) buffer->l2 + data_delta;
+    }
+    if (buffer->l2_5) {
+        new_buffer->l2_5 = (char *) buffer->l2_5 + data_delta;
+    }
+    if (buffer->l3) {
+        new_buffer->l3 = (char *) buffer->l3 + data_delta;
+    }
+    if (buffer->l4) {
+        new_buffer->l4 = (char *) buffer->l4 + data_delta;
+    }
+    if (buffer->l7) {
+        new_buffer->l7 = (char *) buffer->l7 + data_delta;
+    }
+
+    return new_buffer;
 }
 
+/* Creates and returns a new ofpbuf that initially contains a copy of the
+ * 'size' bytes of data starting at 'data' with no headroom or tailroom. */
 struct ofpbuf *
 ofpbuf_clone_data(const void *data, size_t size)
 {
-    struct ofpbuf *b = ofpbuf_new(size);
+    return ofpbuf_clone_data_with_headroom(data, size, 0);
+}
+
+/* Creates and returns a new ofpbuf that initially contains 'headroom' bytes of
+ * headroom followed by a copy of the 'size' bytes of data starting at
+ * 'data'. */
+struct ofpbuf *
+ofpbuf_clone_data_with_headroom(const void *data, size_t size, size_t headroom)
+{
+    struct ofpbuf *b = ofpbuf_new_with_headroom(size, headroom);
     ofpbuf_put(b, data, size);
     return b;
 }
 
 /* Frees memory that 'b' points to, as well as 'b' itself. */
 void
-ofpbuf_delete(struct ofpbuf *b) 
+ofpbuf_delete(struct ofpbuf *b)
 {
     if (b) {
         ofpbuf_uninit(b);
@@ -103,7 +232,7 @@ ofpbuf_delete(struct ofpbuf *b)
  * commonly, the data in a ofpbuf is at its beginning, and thus the ofpbuf's
  * headroom is 0.) */
 size_t
-ofpbuf_headroom(struct ofpbuf *b) 
+ofpbuf_headroom(const struct ofpbuf *b)
 {
     return (char*)b->data - (char*)b->base;
 }
@@ -111,56 +240,151 @@ ofpbuf_headroom(struct ofpbuf *b)
 /* Returns the number of bytes that may be appended to the tail end of ofpbuf
  * 'b' before the ofpbuf must be reallocated. */
 size_t
-ofpbuf_tailroom(struct ofpbuf *b) 
+ofpbuf_tailroom(const struct ofpbuf *b)
 {
     return (char*)ofpbuf_end(b) - (char*)ofpbuf_tail(b);
 }
 
-/* Ensures that 'b' has room for at least 'size' bytes at its tail end,
- * reallocating and copying its data if necessary. */
-void
-ofpbuf_prealloc_tailroom(struct ofpbuf *b, size_t size) 
+static void
+ofpbuf_copy__(struct ofpbuf *b, uint8_t *new_base,
+              size_t new_headroom, size_t new_tailroom)
 {
-    if (size > ofpbuf_tailroom(b)) {
-        size_t new_allocated = b->allocated + MAX(size, 64);
-        void *new_base = xmalloc(new_allocated);
-        uintptr_t base_delta = (char*)new_base - (char*)b->base;
-        memcpy(new_base, b->base, b->allocated);
-        free(b->base);
-        b->base = new_base;
-        b->allocated = new_allocated;
-        b->data = (char*)b->data + base_delta;
+    const uint8_t *old_base = b->base;
+    size_t old_headroom = ofpbuf_headroom(b);
+    size_t old_tailroom = ofpbuf_tailroom(b);
+    size_t copy_headroom = MIN(old_headroom, new_headroom);
+    size_t copy_tailroom = MIN(old_tailroom, new_tailroom);
+
+    memcpy(&new_base[new_headroom - copy_headroom],
+           &old_base[old_headroom - copy_headroom],
+           copy_headroom + b->size + copy_tailroom);
+}
+
+/* Reallocates 'b' so that it has exactly 'new_headroom' and 'new_tailroom'
+ * bytes of headroom and tailroom, respectively. */
+static void
+ofpbuf_resize__(struct ofpbuf *b, size_t new_headroom, size_t new_tailroom)
+{
+    void *new_base, *new_data;
+    size_t new_allocated;
+
+    new_allocated = new_headroom + b->size + new_tailroom;
+
+    switch (b->source) {
+    case OFPBUF_DPDK:
+        OVS_NOT_REACHED();
+
+    case OFPBUF_MALLOC:
+        if (new_headroom == ofpbuf_headroom(b)) {
+            new_base = xrealloc(b->base, new_allocated);
+        } else {
+            new_base = xmalloc(new_allocated);
+            ofpbuf_copy__(b, new_base, new_headroom, new_tailroom);
+            free(b->base);
+        }
+        break;
+
+    case OFPBUF_STACK:
+        OVS_NOT_REACHED();
+
+    case OFPBUF_STUB:
+        b->source = OFPBUF_MALLOC;
+        new_base = xmalloc(new_allocated);
+        ofpbuf_copy__(b, new_base, new_headroom, new_tailroom);
+        break;
+
+    default:
+        OVS_NOT_REACHED();
+    }
+
+    b->allocated = new_allocated;
+    b->base = new_base;
+
+    new_data = (char *) new_base + new_headroom;
+    if (b->data != new_data) {
+        uintptr_t data_delta = (char *) new_data - (char *) b->data;
+        b->data = new_data;
         if (b->l2) {
-            b->l2 = (char*)b->l2 + base_delta;
+            b->l2 = (char *) b->l2 + data_delta;
+        }
+        if (b->l2_5) {
+            b->l2_5 = (char *) b->l2_5 + data_delta;
         }
         if (b->l3) {
-            b->l3 = (char*)b->l3 + base_delta;
+            b->l3 = (char *) b->l3 + data_delta;
         }
         if (b->l4) {
-            b->l4 = (char*)b->l4 + base_delta;
+            b->l4 = (char *) b->l4 + data_delta;
         }
         if (b->l7) {
-            b->l7 = (char*)b->l7 + base_delta;
+            b->l7 = (char *) b->l7 + data_delta;
         }
     }
 }
 
+/* Ensures that 'b' has room for at least 'size' bytes at its tail end,
+ * reallocating and copying its data if necessary.  Its headroom, if any, is
+ * preserved. */
 void
-ofpbuf_prealloc_headroom(struct ofpbuf *b, size_t size) 
+ofpbuf_prealloc_tailroom(struct ofpbuf *b, size_t size)
 {
-    assert(size <= ofpbuf_headroom(b));
+    if (size > ofpbuf_tailroom(b)) {
+        ofpbuf_resize__(b, ofpbuf_headroom(b), MAX(size, 64));
+    }
 }
 
-/* Trims the size of 'b' to fit its actual content. */
+/* Ensures that 'b' has room for at least 'size' bytes at its head,
+ * reallocating and copying its data if necessary.  Its tailroom, if any, is
+ * preserved. */
+void
+ofpbuf_prealloc_headroom(struct ofpbuf *b, size_t size)
+{
+    if (size > ofpbuf_headroom(b)) {
+        ofpbuf_resize__(b, MAX(size, 64), ofpbuf_tailroom(b));
+    }
+}
+
+/* Trims the size of 'b' to fit its actual content, reducing its tailroom to
+ * 0.  Its headroom, if any, is preserved.
+ *
+ * Buffers not obtained from malloc() are not resized, since that wouldn't save
+ * any memory. */
 void
 ofpbuf_trim(struct ofpbuf *b)
 {
-    /* XXX These could be supported, but the current client doesn't care. */
-    assert(b->data == b->base);
-    assert(b->l2 == NULL && b->l3 == NULL && b->l4 == NULL && b->l7 == NULL);
-    if (b->allocated > b->size) {
-        b->base = b->data = xrealloc(b->base, b->size);
-        b->allocated = b->size;
+    ovs_assert(b->source != OFPBUF_DPDK);
+
+    if (b->source == OFPBUF_MALLOC
+        && (ofpbuf_headroom(b) || ofpbuf_tailroom(b))) {
+        ofpbuf_resize__(b, 0, 0);
+    }
+}
+
+/* If 'b' is shorter than 'length' bytes, pads its tail out with zeros to that
+ * length. */
+void
+ofpbuf_padto(struct ofpbuf *b, size_t length)
+{
+    if (b->size < length) {
+        ofpbuf_put_zeros(b, length - b->size);
+    }
+}
+
+/* Shifts all of the data within the allocated space in 'b' by 'delta' bytes.
+ * For example, a 'delta' of 1 would cause each byte of data to move one byte
+ * forward (from address 'p' to 'p+1'), and a 'delta' of -1 would cause each
+ * byte to move one byte backward (from 'p' to 'p-1'). */
+void
+ofpbuf_shift(struct ofpbuf *b, int delta)
+{
+    ovs_assert(delta > 0 ? delta <= ofpbuf_tailroom(b)
+               : delta < 0 ? -delta <= ofpbuf_headroom(b)
+               : true);
+
+    if (delta != 0) {
+        char *dst = (char *) b->data + delta;
+        memmove(dst, b->data, b->size);
+        b->data = dst;
     }
 }
 
@@ -168,7 +392,7 @@ ofpbuf_trim(struct ofpbuf *b)
  * copying its data if necessary.  Returns a pointer to the first byte of the
  * new data, which is left uninitialized. */
 void *
-ofpbuf_put_uninit(struct ofpbuf *b, size_t size) 
+ofpbuf_put_uninit(struct ofpbuf *b, size_t size)
 {
     void *p;
     ofpbuf_prealloc_tailroom(b, size);
@@ -192,25 +416,66 @@ ofpbuf_put_zeros(struct ofpbuf *b, size_t size)
  * is reallocated and copied if necessary.  Returns a pointer to the first
  * byte of the data's location in the ofpbuf. */
 void *
-ofpbuf_put(struct ofpbuf *b, const void *p, size_t size) 
+ofpbuf_put(struct ofpbuf *b, const void *p, size_t size)
 {
     void *dst = ofpbuf_put_uninit(b, size);
     memcpy(dst, p, size);
     return dst;
 }
 
+/* Parses as many pairs of hex digits as possible (possibly separated by
+ * spaces) from the beginning of 's', appending bytes for their values to 'b'.
+ * Returns the first character of 's' that is not the first of a pair of hex
+ * digits.  If 'n' is nonnull, stores the number of bytes added to 'b' in
+ * '*n'. */
+char *
+ofpbuf_put_hex(struct ofpbuf *b, const char *s, size_t *n)
+{
+    size_t initial_size = b->size;
+    for (;;) {
+        uint8_t byte;
+        bool ok;
+
+        s += strspn(s, " \t\r\n");
+        byte = hexits_value(s, 2, &ok);
+        if (!ok) {
+            if (n) {
+                *n = b->size - initial_size;
+            }
+            return CONST_CAST(char *, s);
+        }
+
+        ofpbuf_put(b, &byte, 1);
+        s += 2;
+    }
+}
+
 /* Reserves 'size' bytes of headroom so that they can be later allocated with
  * ofpbuf_push_uninit() without reallocating the ofpbuf. */
 void
-ofpbuf_reserve(struct ofpbuf *b, size_t size) 
+ofpbuf_reserve(struct ofpbuf *b, size_t size)
 {
-    assert(!b->size);
+    ovs_assert(!b->size);
     ofpbuf_prealloc_tailroom(b, size);
     b->data = (char*)b->data + size;
 }
 
+/* Reserves 'size' bytes of headroom so that they can be later allocated with
+ * ofpbuf_push_uninit() without reallocating the ofpbuf. */
+void
+ofpbuf_reserve_with_tailroom(struct ofpbuf *b, size_t headroom,
+                             size_t tailroom)
+{
+    ovs_assert(!b->size);
+    ofpbuf_prealloc_tailroom(b, headroom + tailroom);
+    b->data = (char*)b->data + headroom;
+}
+
+/* Prefixes 'size' bytes to the head end of 'b', reallocating and copying its
+ * data if necessary.  Returns a pointer to the first byte of the data's
+ * location in the ofpbuf.  The new data is left uninitialized. */
 void *
-ofpbuf_push_uninit(struct ofpbuf *b, size_t size) 
+ofpbuf_push_uninit(struct ofpbuf *b, size_t size)
 {
     ofpbuf_prealloc_headroom(b, size);
     b->data = (char*)b->data - size;
@@ -218,8 +483,22 @@ ofpbuf_push_uninit(struct ofpbuf *b, size_t size)
     return b->data;
 }
 
+/* Prefixes 'size' zeroed bytes to the head end of 'b', reallocating and
+ * copying its data if necessary.  Returns a pointer to the first byte of the
+ * data's location in the ofpbuf. */
 void *
-ofpbuf_push(struct ofpbuf *b, const void *p, size_t size) 
+ofpbuf_push_zeros(struct ofpbuf *b, size_t size)
+{
+    void *dst = ofpbuf_push_uninit(b, size);
+    memset(dst, 0, size);
+    return dst;
+}
+
+/* Copies the 'size' bytes starting at 'p' to the head end of 'b', reallocating
+ * and copying its data if necessary.  Returns a pointer to the first byte of
+ * the data's location in the ofpbuf. */
+void *
+ofpbuf_push(struct ofpbuf *b, const void *p, size_t size)
 {
     void *dst = ofpbuf_push_uninit(b, size);
     memcpy(dst, p, size);
@@ -229,7 +508,7 @@ ofpbuf_push(struct ofpbuf *b, const void *p, size_t size)
 /* If 'b' contains at least 'offset + size' bytes of data, returns a pointer to
  * byte 'offset'.  Otherwise, returns a null pointer. */
 void *
-ofpbuf_at(const struct ofpbuf *b, size_t offset, size_t size) 
+ofpbuf_at(const struct ofpbuf *b, size_t offset, size_t size)
 {
     return offset + size <= b->size ? (char *) b->data + offset : NULL;
 }
@@ -237,15 +516,15 @@ ofpbuf_at(const struct ofpbuf *b, size_t offset, size_t size)
 /* Returns a pointer to byte 'offset' in 'b', which must contain at least
  * 'offset + size' bytes of data. */
 void *
-ofpbuf_at_assert(const struct ofpbuf *b, size_t offset, size_t size) 
+ofpbuf_at_assert(const struct ofpbuf *b, size_t offset, size_t size)
 {
-    assert(offset + size <= b->size);
+    ovs_assert(offset + size <= b->size);
     return ((char *) b->data) + offset;
 }
 
 /* Returns the byte following the last byte of data in use in 'b'. */
 void *
-ofpbuf_tail(const struct ofpbuf *b) 
+ofpbuf_tail(const struct ofpbuf *b)
 {
     return (char *) b->data + b->size;
 }
@@ -253,14 +532,14 @@ ofpbuf_tail(const struct ofpbuf *b)
 /* Returns the byte following the last byte allocated for use (but not
  * necessarily in use) by 'b'. */
 void *
-ofpbuf_end(const struct ofpbuf *b) 
+ofpbuf_end(const struct ofpbuf *b)
 {
     return (char *) b->base + b->allocated;
 }
 
 /* Clears any data from 'b'. */
 void
-ofpbuf_clear(struct ofpbuf *b) 
+ofpbuf_clear(struct ofpbuf *b)
 {
     b->data = b->base;
     b->size = 0;
@@ -269,10 +548,10 @@ ofpbuf_clear(struct ofpbuf *b)
 /* Removes 'size' bytes from the head end of 'b', which must contain at least
  * 'size' bytes of data.  Returns the first byte of data removed. */
 void *
-ofpbuf_pull(struct ofpbuf *b, size_t size) 
+ofpbuf_pull(struct ofpbuf *b, size_t size)
 {
     void *data = b->data;
-    assert(b->size >= size);
+    ovs_assert(b->size >= size);
     b->data = (char*)b->data + size;
     b->size -= size;
     return data;
@@ -282,7 +561,56 @@ ofpbuf_pull(struct ofpbuf *b, size_t size)
  * head end of 'b' and returns the first byte removed.  Otherwise, returns a
  * null pointer without modifying 'b'. */
 void *
-ofpbuf_try_pull(struct ofpbuf *b, size_t size) 
+ofpbuf_try_pull(struct ofpbuf *b, size_t size)
 {
     return b->size >= size ? ofpbuf_pull(b, size) : NULL;
 }
+
+/* Returns the data in 'b' as a block of malloc()'d memory and frees the buffer
+ * within 'b'.  (If 'b' itself was dynamically allocated, e.g. with
+ * ofpbuf_new(), then it should still be freed with, e.g., ofpbuf_delete().) */
+void *
+ofpbuf_steal_data(struct ofpbuf *b)
+{
+    void *p;
+    ovs_assert(b->source != OFPBUF_DPDK);
+
+    if (b->source == OFPBUF_MALLOC && b->data == b->base) {
+        p = b->data;
+    } else {
+        p = xmemdup(b->data, b->size);
+        if (b->source == OFPBUF_MALLOC) {
+            free(b->base);
+        }
+    }
+    b->base = b->data = NULL;
+    return p;
+}
+
+/* Returns a string that describes some of 'b''s metadata plus a hex dump of up
+ * to 'maxbytes' from the start of the buffer. */
+char *
+ofpbuf_to_string(const struct ofpbuf *b, size_t maxbytes)
+{
+    struct ds s;
+
+    ds_init(&s);
+    ds_put_format(&s, "size=%"PRIuSIZE", allocated=%"PRIuSIZE", head=%"PRIuSIZE", tail=%"PRIuSIZE"\n",
+                  b->size, b->allocated,
+                  ofpbuf_headroom(b), ofpbuf_tailroom(b));
+    ds_put_hex_dump(&s, b->data, MIN(b->size, maxbytes), 0, false);
+    return ds_cstr(&s);
+}
+
+/* Removes each of the "struct ofpbuf"s on 'list' from the list and frees
+ * them.  */
+void
+ofpbuf_list_delete(struct list *list)
+{
+    struct ofpbuf *b, *next;
+
+    LIST_FOR_EACH_SAFE (b, next, list_node, list) {
+        list_remove(&b->list_node);
+        ofpbuf_delete(b);
+    }
+}